1. Field of the Invention
This invention relates generally to an editing system, and is directed more particularly to a system which provides an address signal used for recording a video signal into the vertical blanking period of which the address signal is inserted.
2. Description of the Prior Art
In order to achieve an edition of a video and/or audio signal speedily and precisely, in the art there is proposed a method of recording an address-signal on a magnetic tape in addition to a video and/or audio signal. In this case, as the address signal there are present signals of various codes, but the SMPTE time code signal is recommended as an American National Standard and the EBU time code signal is recommended as a standard code for 625 - line/50 - field television tape-recordings. In the art, the above two time code signals are coded on a record medium along its longitudinal tracks and the readout of the signals can be achieved at tape speeds from slow to high speed. In the case where the record medium is stopped or transported at a very low speed, the reproduction of time code signals becomes impossible. In fact, upon editing a video tape by a video tape recorder its merit is that an editor can choose individual frames presented visually at very low tape speeds, but there occurs such a demerit in this case that the address of a choosen frame can not be known.
The time code signals identify each television frame, but the identification of its even or odd field and that of the phase of the burst signal of each television field are impossible. Therefore, no precise editing can be achieved by the above prior art.
In order to remove the above defects, the inventor of this invention has proposed such a method to insert an address signal, which will be referred to as a VITC (vertical interval time code) signal, in a vertical blanking period of a video signal in the copending application U.S. Ser. No. 819,172, filed on July 26, 1977 U.S. Pat. No. 4,134,130. If both the VITC signal and longitudinal track time code signal such as the well-known SMPTE time code recorded on a longitudinal track of a magnetic tape are used, the address of a video signal can be always known regardless of transportation speeds of the tape.
However, it is necessary that when insert editing or assemble editing is carried out, the VITC and longitudinal track time code of video signals which are newly recorded should be made such codes continuous to those of video signals which were recorded previously.